Compact positive displacement pump

ABSTRACT

A positive displacement pump adapted especially for pumping oil in a power steering system for an automotive vehicle, said pump comprising a rotor, slipper elements in the rotor engageable with the cam surface of a relatively stationary pump cam, a pump body surrounding the cam and having internal cavities which define a high-pressure outlet region, the low-pressure fluid inlet region of the pump being defined by other parts of the stationary housing, a reservoir surrounding the pump body and cooperating with a pump pressure plate which is subjected to a supercharge pressure obtained by the velocity pressure of fluid bypassed from a fluid control valve situated in the pump body.

United States Patent [72] Inventors [21 Appl. No. [22] Filed [45] Patented [73] Assignee [54] COMPACT POSITIVE DISPLACEMENT PUMP 3 Claims, 8 DrawingFigs.

[52] US. (I 4l7/79, 417/87, 417/310 [51] Int. Cl ..F04b 23/04, F04b 49/00 [50] Field of Search 417/87, 310, 79; 418/262, 15

[56] References Cited UNITED STATES PATENTS 2,858,766 11/1958 Toschkoff 417/79 2,887,060 5/1959 Adams et a1. 417/79 2,983,226 5/1961 Livermore 417/79 FOREIGN PATENTS 654,271 12/1962 Canada 417/310 Primary Examiner-Carlton R. Croyle Assistant Examiner-Richard E. Gluch Attorneys--John R. Faulkner and Donald J. Harrington ABSTRACT: A positive displacement pump adapted especially for pumping oil in a power steering system for an automotive vehicle, said pump comprising a rotor, slipper elements in the rotor engageable with the cam surface of a relatively stationary pump cam, a pump body surrounding the cam and having internal cavities which define a high-pressure outlet region, the low-pressure fluid inlet region of the pump being defined by other parts of the stationary housing, a reservoir surrounding the pump body and cooperating with a pump pressure plate which is subjected to a. supercharge pressure obtained by the velocity pressure of tfluid bypassed from a fluid control valve situated in the pump body.

PATENTEUum 19 Ian 3. 6 l 4. 266 SHEET 2 0r 6 Z A. a

PATENTEDum 19 I9?! SHEET 6 OF 6 a2 94 .96 9a a m 2'06 INVENTORfi F/Fffi /9. 5/19/71 1? jffi/a' u M62206 Arm m Y5.

COMPACT POSITIVE DISPLACEMENT PUMP GENERAL DESCRIPTION OF THE INVENTION The improvements of our invention are adapted to be used in fluid pressure pumps for power steering system in automotive vehicles. They include pump components that are arranged in a component fashion to form a pump assembly of reduced dimensions thereby making it possible to package the pump assembly conveniently in a vehicle engine compartment where it may be driven by a belt and pulley arrangement connected to the engine crankshaft. It is possible, however, that other means for driving the rotor of the pump also may be used without departing from the teachings of our invention.

The pump assembly of our invention comprises a rotor having peripheral slots in which are positioned pumping slippers which are adapted to contact the cam surface of a surrounding cam member. The cam surface is formed with a generated profile which deviates from the curvature of the periphery of the rotor in a precise, controlled fashion whereby the slippers are caused to reciprocate radially inwardly and outwardly as the rotor is rotated about its axis. The cam member cooperates with the rotor to define a pair of oppositely displaced pumping chambers whereby hydrostatic forces acting on the rotor are substantially balanced thereby reducing or eliminating transverse bearing loads on the rotor due to the development of hydrostatic pressure forces.

Each pumping chamber is provided with inlet porting and outlet porting. The outlet porting, which is in the high-pressure side of the pump, is formed by means of internal cored passages formed in the pump housing surrounding the cam member. The can member and the rotor are located in the pump housing and are separated from the high-pressure porting by a first and lower pressure plate. The cam, together with the pressure plate, is held in assembled fixed relationship by means of a pin.

Internal passages conduct pressure from the high-pressure cavities in the pump housing to a fluid flow control valve assembly situated also in the pump housing as part of the internal pump assembly. The fluid flow control valve establishes a predetermined rate of flow from the pump regardless of the rate at which the rotor is rotated relative to the cam member. Any excess fluid not delivered to the outlet passage of the pump assembly is bypassed through a bypass passage, which in turn communicates with a lowpressure region of the pump surrounding the cam member. The velocity head of the moving fluid in the bypass flow passage is used to supercharge the fluid in the low-pressure region of the circuit.

A reservoir surrounding the pump housing is defined in part by an end cover. Fluid is drawn from the reservoir into the low-pressure inlet region of the pump assembly by the aspirating action of the flow in the bypass passage of the flow control valve assembly. The supercharge pressure developed by this aspirating action, which is related functionally to the magnitude of the velocity pressure in the bypass flow passage, is distributed to a second or upper pressure plate which engages the so-called pump body, the latter comprises the cam member and the rotor with the reciprocating slippers.

The supercharged portion of the low-pressure region is sealed from the main reservoir regions. A bolt or some other suitable fastening device is used to maintain the two pressure plates and the pump body in fixed, assembled relationship with respect to the pump housing.

By isolating the high-pressure region of the pump assembly within the pump housing, high-pressure forces, acting on pressure plates is avoided and the deflections often due to such loading are eliminated.

The provision of a pump assembly having the foregoing characteristics is an object of our invention. It is a further ob-' ject of our invention to provide a pump assembly of the type i set forth in the preceding paragraphs and which is characterized also by reduced overall dimensions.

BRIEF DESCRIPTION OF THE FIGURES OF THE DRAWING FIG. ll shows a longitudinal cross-sectional view, partly in elevation, of our improved pump assembly. This view is taken along the plane of section line 1l-ll of FIG. 2..

FIG. 2 is a cross sectional view of the pump in FIG. I as seen from the plane of section line 2-2 of FIG. 11.

FIG. 3 is another cross-sectional view of the pump of FIG. I as seen from the plane of section line 2-3 in FIGS. I, t and 5.

FIG. 4 is a cross-sectional view taken along the plane of section line ll-4i of FIG. 3|.

7 FIG. 5 is a cross sectional view talten along the plane of section line 5-5 of FIG. 3.

FIG. 6 is a cross-sectional view taken along the plane of section line 6-6 of FIG. I.

FIG. '7 is an assembly view of a rotor, the slippers and the cam member for the assembly of FIG. 1.

FIG. 8 is a cross sectional view taken along section line b% of FIG. 7.

PARTICULAR DESCRIPTION OF THE INVENTION Numeral It designates a pump housing that may be secured by bracket 12 to the vehicle engine block or to some other suitable structure in the vehicle engine compartment. The embodiment described in this specification is adapted especially to be used in a power steering system for an automotive vehi cle.

Housing III has a pump cavity Id which is formed with a flat surface against which lower pressure plate In is positioned.

Housing III is formed with a driveshaft opening 118 within which is positioned driveshaft 20. Shaft 20 is journaled by bushing 22 within the opening I8.

At the radially inward end of the shaft 20 there is formed a shoulder M, which is adapted to engage the inner side of the lower pressure plate I6 thereby allowing the thrust forces acting on the shaft 20 to be distributed to the pump housing It] through the pressure plate I6. An upper pressure plate 26 is situated adjacent the end of the shaft 20 as shown at 23. A cam member 30, with circular outside dimensions is situated between the plates I6 and 26.

The cavity 114 in the pump housing It is formed with internal threads 32 to accommodate a spanner nut 34 which is threaded into the cavity 141 to retain the pressure plates 26 and I6 and the cam member M) in assembled, stacked relation- Ship.

A pump rotor 36 is rotatably positioned within the cam member 30. This is best seen in FIG. 7. Rotor 36 is formed with a splined, central opening 38 in which the end of the shaft 20 is positioned. The shaft end is formed with external splines which drivably engage the internal splines of opening 38.

The rotor 36, which is circular, establishes the seal with cam member 30 at the uppermost location ilt) and a lowermost location 42. The internal cam surface of the cam member 30 deviates from the curvature of the rotor at other angular positions to define a pair of opposed worlcing chambers identified in FIG-7 by reference characters M and A6. The contour of the cam surface for the cam member 30 is formed with a shape that contributes to pump efficiency and minimum noise. The cam surface is engaged by the radially outward surfaces of pumping elements in the form of slippers 48.

There are eight slippers in the embodiment shown in FIG. 7. Each is received within a slipper pocket 50 in which it may oscillate angularly as well as reciprocate in a radial direction. Each slipper is urged radially outwardly into engagement with the surrounding cam surface by a slipper spring 52, which is seated on the rotor 36. i

As viewed in FIG. '7, the rotor rotates in a counterclockwise direction. The leading edge of each slipper is slotted as shown at 55 to permit equalization of pressure in the radially inward region of the slipper pocket and in the working chambers M and d6. These chambers communicate with high-pressure outlet cavity 54 and high-pressure outlet cavity 56. Communication is established with these cavities through porting.

A high-pressure port 58 formed in the lower pressure plate 16 is indicated in FIG. 1. It is in communication with each of the high-pressure cavities 56 and 54. The high-pressure cavities 56 and 54 are connected to each other through internal passage structure in the housing 10. Chamber 60 communicates with a corresponding chamber 62 formed l80 out of position as indicated in FIG. 3. Chambers 60 and 62 are joined together by an annular space 64 which surrounds the cam member 30. Annular space 64 is formed by an annular recess fonned in the housing 10. This recess, together with the chambers 60 and 62, forms the low-pressure region of the pump circuit. Cavities 60 and 62 serve as lower pressure inlet ports which communicate with the working chambers 44 and 46.

Port 58 serves as one of the outlet ports. A corresponding port in the lower plate 16, which communicates with the cavity 56, forms the other outlet port. Each of the working chambers 44 and 46 has an inlet port and an outlet port.

The housing is internally cored to provide a high-pressure port extension 66, which communicates with the valve chamber 68. This communication is established with the valve chamber 68 at the location of annular space 70 indicated in FIGS. 3 and 6.

An externally threaded orifice member 72 is received within an internally threaded portion of the chamber 68. It carries an orifice element 74 at its interrnost end. This orifice element is formed with a precalibrated flow control orifice 76 through which fluid discharged into the annular space 70 is allowed to pass. The fluid, which passes through the orifice 76, enters internal pressure delivery passage 78 in the member 72. The pressure in passage 78 is distributed through a flow orifice 80 into internal passage 82, which communicates with spring chamber 84 at one end of the valve chamber 68. A spring 86 located in the spring chamber 84 acts on a movable sleeve 88. It normally tends to urge the sleeve 88 toward the orifice member 72. Sleeve 88 carries a tapered valve element 90 which is received in the orifice 76. When the sleeve 88 is positioned at a location adjacent the orifice 76, maximum flow area is provided through the orifice 76. If the sleeve 88 is moved against the force of spring 86, the flow area through the orifice 76 is progressively restricted by the tapered valve element 90.

Valve element 90 and the cooperating orifice serve as a flow control valve. If the flow to the inner space 70 is increased, the pressure drop across the orifice 76 is increased. This causes the sleeve 88 to move against the force of spring 86, thereby restricting the flow through the orifice 76. The net output flow in the passage 78, which communicates with the pump outlet conduit, is reduced to a value determined by the calibration of the valve element 90'.

The outlet flow in pressure passage 78 is determined by the spring 86 because of the action of the orifice 80. If this pressure exceeds a predetermined value, a one-way flow relief valve element 92 becomes unseated thereby establishing a bypass flow path to annular space 94 surrounding the sleeve 88. This space, in turn, communicates with nozzle element 96. The bypass flow is accelerated by the nozzle element 96 and discharged into the annular space 64 surrounding the member 30. This provides a velocity pressure which supercharges the fluid in the annular space 64. Because the static pressure in the path of the accelerated fluid passing through the nozzle 96 is less than ambient pressure, fluid is drawn by the aspirator action thus produced through internal feed passage 98, which communicates with reservoir chamber 100.

Reservoir chamber 100 is defined by a reservoir cover 102 which surrounds the housing 10. The cover 102 is sealed by a circular seal 104. The end plate 106 of the cover 102 extends across the cavity 14 outside of the upper pressure plate 26. The upper end of the reservoir communicates with a filler tube 108 which has a suitable inlet to permit filling of the reservoir. A circular gasket seal 110 is positioned between the end wall 106 of the cover 102 and the end of the housing 10 thereby isolating the space between the wall 106 and the pressure plate 26 from the reservoir itself. This space is in fluid communication with the annular space 64 surrounding the member 30. Thus, this space is maintained at a higher pressurethan the inlet fluid pressure. A differential pressure is possible because of the sealing action of the seal 1 10.

The supercharge action developed by the velocity pressure in the bypass flow path for the flow control valve helps to avoid cavitation in the pump and it contributes to the overall operating efficiency of the pump It also makes possible a reduced reservoir size.

The isolated location of the high-pressure chambers 54 and 56 in the housing 10 eliminates pressure loading in pumps of this type, which is caused by hydrostatic loading of the elements of the pump such as the pressure plates. If the highpressure side of the pump were to be in fluid communication with the pressure plates, a certain amount of deflection would occur and this, in turn, would afiect the pump clearances and tolerances. This in turn would afi'ect adversely the overall operating efficiency of the pump.

Having described a preferred embodiment of our invention, what we claim and desire to secure by U.S. Letters Patent is:

l. A positive displacement fluid pump comprising a pump rotor and pumping elements located on the periphery thereof, a pump cam member having a cam surface surrounding said rotor with the pumping elements slidably engaging said cam surface thereby defining pumping chambers, a housing surrounding said cam member, high-pressure passages formed in said housing where they are semi-isolated from said rotor, a first pressure plate located in said housing intermediate one side of said rotor and the adjacent walls of said housing, high pressure outlet ports in said pressure plate establishing communication between said pumping chambers in said earn member and said high-pressure passages in said housing, a second pressure plate adjacent the opposite side of said rotor, inlet ports in one of said pressure plates, a low-pressure inlet chamber formed in part in said housing in fluid communication with said inlet ports, flow control valve means in said housing including a pressure delivery passage and a fluid bypass passage, said valve means being adapted to divide the flow from said outlet ports to said pressure delivery passage and to said bypass passage, the percentage of flow distributed to said bypass passage increasing upon an increase in the pressure in said outlet ports, said flow control valve means including a nozzle portion directing bypass flow to a said low-pressure inlet chamber thus supercharging said inlet ports, a cover extending over one side of said housing and cooperating with said housing to define a low-pressure reservoir, an end wall of said cover sealingly engaging said housing and cooperating with said second pressure plate to define a supercharged pressure cavity in fluid communication with said low-pressure inlet chamber, and internal pressure passage structure formed in said housing establishing fluid communication between said low-pressure chamber and said reservoir, the aspirator action due to the movement of fluid in said nozzle portion inducing flow from said reservoir chamber to said low-pressure inlet chamber.

2. A positive displacement fluid pump comprising a pump rotor and pumping elements located on the periphery thereof, a pump cam member having a cam surface surrounding said rotor with the pumping elements slidably engaging said cam surface thereby defining pumping chambers, a housing surrounding said cam member, high-pressure passages formed in said housing where they are semiisolated from said rotor, a first pressure plate located in said housing intermediate one side of said rotor and the adjacent wall of said housing, highpressure outlet ports in said first pressure plate establishing communication between said pumping chambers in said cam member and said high-pressure passages in said housing, a second pressure plate adjacent the opposite side of said rotor, inlet ports in said second pressure plate, a low-pressure inlet chamber formed in part in said housing in fluid communication with said inlet ports, flow control valve means in said housing including a pressure delivery passage and a fluid bypass passage, said valve means being adapted to divide the flow from said outlet ports to said pressure delivery passage and to said bypass passage, the percentage of flow distributed to said bypass passage increasing upon an increase in the pressure in said outlet ports, said flow control valve means including a nozzle portion directing bypass flow to said low-pressure inlet chamber thus supercharging inlet chamber, a cover extending over one side of said housing and cooperating with said housing to define a low-pressure reservoir, internal pressure passage structure fonned in said housing establishing a fluid communication between said low-pressure inlet chamber and said reservoir, the aspirator action due to the movement of fluid in said nozzle portion inducing flow from said reservoir to said low-pressure inlet chambers, a second pressure plate located adjacent said cam member remote from said high-pressure chambers in said housing, a retainer secured within said housing and acting on said second pressure plate to hold said pressure plates and said cam member in fixed, axially stacked relationship, said reservoir comprising an end plate located adjacent said second pressure plate, said end plate and said second pressure plate defining a supercharged pressure cavity, and means for sealing the reservoir from said supercharged pressure cavity, said supercharged pressure cavity communicating with said low-pressure inlet chamber.

3. The combination as set forth in claim 2 wherein said nozzle portion is situated in and partly defines said bypass passage, the discharge side of said nozzle portion being adapted to direct fluid into said low-pressure inlet chamber whereby said low-pressure inlet chamber and said supercharged pressure cavity are supercharged with the velocity pressure caused by the acceleration of fluid through said nozzle portion. 

1. A positive displacement fluid pump comprising a pump rotor and pumping elements located on the periphery thereof, a pump cam member having a cam surface surrounding said rotor with the pumping elements slidably engaging said cam surface thereby defining pumping chambers, a housing surrounding said cam member, high-pressure passages formed in said housing where they are semi-isolated from said rotor, a first pressure plate located in said housing intermediate one side of said rotor and the adjacent walls of said housing, high-pressure outlet ports in said pressure plate establishing communication between said pumping chambers in said cam member and said high-pressure passages in said housing, a second pressure plate adjacent the opposite side of said rotor, inlet ports in one of said pressure plates, a lowpressure inlet chamber formed in part in said housing in fluid communication with said inlet ports, flow control valve means in said housing including a pressure delivery passage and a fluid bypass passage, said valve means being adapted to divide the flow from said outlet ports to said pressure delivery passage and to said bypass passage, the percentage of flow distributed to said bypass passage increasing upon an increase in the pressure in said outlet ports, said flow control valve means including a nozzle portioN directing bypass flow to a said low-pressure inlet chamber thus supercharging said inlet ports, a cover extending over one side of said housing and cooperating with said housing to define a low-pressure reservoir, an end wall of said cover sealingly engaging said housing and cooperating with said second pressure plate to define a supercharged pressure cavity in fluid communication with said low-pressure inlet chamber, and internal pressure passage structure formed in said housing establishing fluid communication between said low-pressure chamber and said reservoir, the aspirator action due to the movement of fluid in said nozzle portion inducing flow from said reservoir chamber to said low-pressure inlet chamber.
 2. A positive displacement fluid pump comprising a pump rotor and pumping elements located on the periphery thereof, a pump cam member having a cam surface surrounding said rotor with the pumping elements slidably engaging said cam surface thereby defining pumping chambers, a housing surrounding said cam member, high-pressure passages formed in said housing where they are semiisolated from said rotor, a first pressure plate located in said housing intermediate one side of said rotor and the adjacent wall of said housing, high-pressure outlet ports in said first pressure plate establishing communication between said pumping chambers in said cam member and said high-pressure passages in said housing, a second pressure plate adjacent the opposite side of said rotor, inlet ports in said second pressure plate, a low-pressure inlet chamber formed in part in said housing in fluid communication with said inlet ports, flow control valve means in said housing including a pressure delivery passage and a fluid bypass passage, said valve means being adapted to divide the flow from said outlet ports to said pressure delivery passage and to said bypass passage, the percentage of flow distributed to said bypass passage increasing upon an increase in the pressure in said outlet ports, said flow control valve means including a nozzle portion directing bypass flow to said low-pressure inlet chamber thus supercharging inlet chamber, a cover extending over one side of said housing and cooperating with said housing to define a low-pressure reservoir, internal pressure passage structure formed in said housing establishing a fluid communication between said low-pressure inlet chamber and said reservoir, the aspirator action due to the movement of fluid in said nozzle portion inducing flow from said reservoir to said low-pressure inlet chambers, a second pressure plate located adjacent said cam member remote from said high-pressure chambers in said housing, a retainer secured within said housing and acting on said second pressure plate to hold said pressure plates and said cam member in fixed, axially stacked relationship, said reservoir comprising an end plate located adjacent said second pressure plate, said end plate and said second pressure plate defining a supercharged pressure cavity, and means for sealing the reservoir from said supercharged pressure cavity, said supercharged pressure cavity communicating with said low-pressure inlet chamber.
 3. The combination as set forth in claim 2 wherein said nozzle portion is situated in and partly defines said bypass passage, the discharge side of said nozzle portion being adapted to direct fluid into said low-pressure inlet chamber whereby said low-pressure inlet chamber and said supercharged pressure cavity are supercharged with the velocity pressure caused by the acceleration of fluid through said nozzle portion. 